Admin Bar is a sticky bar on the top of your screen that contains useful links for the administrators such as add a New Post, Edit Comments, Edit your Profile, and many more. It can be extended by plugins to add additional functionality, for example, SEO and more. The admin bar was added to WordPress in version 3.1. For registered users, the admin bar is turned on for both viewing the site or the WordPress Admin Area (Dashboard). However, you can turn it off by going to Users » Your Profile.

How to disable Admin Bar from WordPress menu